Gas turbines typically include components which operate at high speeds and are subjected to high mechanical loads at elevated temperatures. Proper and efficient operation of such turbines require precision in placement and relative orientation of the components, particularly the turbine airfoils.
Typically, in the industrial gas turbine (IGT) industry, this requires checking the measurement of the minimum distance (“throat”) between two adjacent airfoils to ensure that proper airfoil positions are maintained. Such measurements are typically made at three radial positions, perpendicular to the trailing edge of an airfoil, with each turbine typically having a large number of such spaced airfoils.
Heretofore, such measurements have typically been taken by first wedging either adjustable parallels or telescoping gauges into the expected throat position, and then maintaining those parallels/gauges in that position for subsequent measurement with Vernier calipers or micrometers.
This technique can be time consuming, requiring not only positioning the parallels/gauges properly, but then separately measuring the parallels/gauges, with the results of such technique often being user dependent. Further, if the position of the parallels/gauges is not adequately maintained prior to measurement (by, e.g., a micrometer), added time can be required to reposition the parallels/gauges for each such measurement. Of course, if it is not noticed that the position is not properly maintained prior to measuring, this can also yield incorrect measurements. In fact, dimensional repeatability errors of 15-25% of the applicable tolerance have been found to occur even between skilled operators,
The present invention is directed toward improving upon the efficiency and reliability of measuring between turbine airfoils.